Molecular foundations of cancer: new targets for intervention.

Conceptual and practical advances in molecular medicine are changing our understanding of cancer pathogenesis. In time this should provide the opportunity to alter the natural history of many cancers.

Induction of acute lymphocytic leukemia differentiation by maintenance therapy.

Despite extensive study in many malignancies, maintenance therapy has clinically benefited only two diseases: acute lymphocytic leukemia (ALL) and acute promyelocytic leukemia (APL). ALL maintenance therapy utilizes low-dose 6-mercaptopurine (6MP) and methotrexate (MTX), while maintenance in APL primarily consists of all-trans-retinoic acid (ATRA). 6MP and MTX as used in ALL are also now usually added to maintenance ATRA for APL, based on data suggesting an improved disease-free survival. Although the mechanism of action of MTX and 6MP as maintenance is unknown, low-dose cytotoxic agents are potent inducers of differentiation in vitro. Thus, we studied whether maintenance therapy in ALL, like ATRA in APL, may be inducing terminal differentiation of ALL progenitors. The APL cell line NB4, the ALL cell lines REH and RS4;11, and patients' ALL blasts were incubated with ATRA, 6MP, and MTX in vitro. All three drugs inhibited the clonogenic growth of the APL and ALL cell lines without inducing immediate apoptosis, but associated with induction of phenotypic differentiation. The three drugs similarly upregulated lymphoid antigen expression, while decreasing CD34 expression, on patients' ALL blasts. These data suggest that induction of leukemia progenitor differentiation plays an important role in the mechanism of action of maintenance therapy in ALL.

JAK2 V617F is a rare finding in de novo acute myeloid leukemia, but STAT3 activation is common and remains unexplained.

Signal transducer and activator of transcription (STAT) proteins are phosphorylated and activated by Janus kinases (JAKs). Recently, several groups identified a recurrent somatic point mutation constitutively activating the hematopoietic growth factor receptor-associated JAK2 tyrosine kinase in diverse chronic myeloid disorders - most commonly classic myeloproliferative disorders (MPD), especially polycythemia vera. We hypothesized that the JAK2 V617F mutation might also be present in samples from patients with acute myeloid leukemia (AML), especially erythroleukemia (AML-M6) or megakaryoblastic leukemia (AML-M7), where it might mimic erythropoietin or thrombopoietin signaling. First, we documented STAT3 activation by immunoblotting in AML-M6 and other AML subtypes. Immunoperoxidase staining confirmed phosphorylated STAT3 in malignant myeloblasts (21% of cases, including all AML-M3 samples tested). We then analyzed genomic DNA from 162 AML, 30 B-cell lymphoma, and 10 chronic lymphocytic leukemia (CLL) samples for JAK2 mutations, and assayed a subset for SOCS1 and FLT3 mutations. Janus kinase2 V617F was present in 13/162 AML samples (8%): 10/13 transformed MPD, and three apparent de novo AML (one of 12 AML-M6, one of 24 AML-M7, and one AML-M2 - all mixed clonality). FLT3 mutations were present in 5/32 (16%), while SOCS1 mutations were totally absent. Lymphoproliferative disorder samples were both JAK2 and SOCS1 wild type. Thus, while JAK2 V617F is uncommon in de novo AML and probably does not occur in lymphoid malignancy, unexplained STAT3 activation is common in AML. Janus kinase2 extrinsic regulators and other proteins in the JAK-STAT pathway should be interrogated to explain frequent STAT activation in AML.

Fluorescent in situ hybridization (FISH) in bone marrow and peripheral blood of leukemia patients: implications for occupational surveillance.

Although there has been a rapid rise in the application of fluorescent in situ hybridization (FISH) analysis of bone marrow tissue for the staging and prognosis determination of hematopoietic malignacies such as the chronic and acute leukemias, it's application as a surveillance tool for leukemogen exposed high risk occupational cohorts is understandably limited by the invasiveness of sample collection. While some small occupational studies have been performed using FISH in peripheral blood with promising results, some of the basic assumptions made in utilizing the FISH technique have not been fully explored. These include selection of the correct hematopoietic cell to assay (myeloid or lymphoid); selection of appropriate chromosomal markers and the sensitivity of peripheral blood FISH in detecting unbalanced genomic abnormalities. In this study, we performed a pilot 'validation' exercise utilizing the FISH technique and standard metaphase cytogenetics, comparing results in tandem pairs of peripheral blood with bone marrow cells, where clonal abnormalities arise. Samples were taken from patients with known chromosomal lesions associated with active leukemia. We carefully chose markers most frequently associated with leukemogen-inducing DNA damage and probes that have been utilized successfully in clinical practice. Ten de novo or therapy-related acute myeloid leukemia (t-AML) patients underwent bone marrow cell karyotyping and fluorescent in situ hybridization (FISH) analysis. Parallel peripheral blood samples were concommitently drawn and evaluated with FISH using the same probes. In six of eight paired samples treated with a 3-day phytohemagglutinin (PHA) stimulation, typically used to assay lymphocytes and their progenitors, we detected abnormal clones. In one of the two remaining cases, we identified an abnormal clone in both bone marrow and PHA-stimulated peripheral blood, although at a level in the peripheral blood sample that would typically be reported as "non-diagnostic" for clinical purposes. These results suggest that use of FISH in PHA stimulated peripheral blood samples with probes commonly employed in t-AML evaluations (chromosomes 5q, 7q, 8, 11q) to detect cytogenetic abnormalities in peripheral blood represents a potentially promising though as yet, under-utilized approach for the occupational surveillance of workers exposed to leukemogens, especially if it could be linked to automated high-throughput assays for increased sensitivity.

New avenues of translational research in leukemia and lymphoma: outgrowth of a Leukemia Society of America-National Cancer Institute workshop.

The workshop was organized on the premise that truly innovative approaches are needed if we are to significantly change the clinical outcomes for leukemias and lymphomas. Several new concepts and pioneering approaches surfaced during the workshop discussions, as summarized above. The design and implementation of translational clinical trials that emphasize these innovative strategies were encouraged as a way to test the concepts put forward at the workshop. Representatives of the Leukemia Society of America and the National Cancer Institute plan to continue their dialogue to develop recommendations regarding the priorities for linked clinical-laboratory investigations on the hematopoietic malignancies and the optimal ways in which to foster such translational research. To this end, the explosion in basic science discoveries during the last two decades and especially during the last 5 years is producing a critical mass of knowledge. This knowledge, in turn, allows us to view leukemia from new perspectives that span molecular pathogenesis, epidemiology, early detection of minimal disease, and the selective targeting of critical leukemogenic mechanisms for therapeutic and ultimately preventive purposes. As in previous decades, during which leukemia has served as the testing ground for precedent-setting concepts of curative therapy (dose-intensity, non-cross-resistance-inducing combinations and aggressive therapy in the minimal residual disease state), leukemia should again serve as a clinical beacon for the identification and exploitation of new molecular targets for therapy. Any impact on curability and duration and quality of survival will be achieved only by building on the cumulative knowledge accrued at multiple levels--molecular and cellular levels as well as in the intact patient--and augmenting the momentum of the bidirectional exchange of information between the laboratory and the clinic that has characterized leukemia research from its incipience. The challenge is formidable and worthy of our most creative and concerted efforts.

Isokinetic gradient sedimentation of normal human bone marrow cells: a simple method for isolation of proliferative granulocytic and erythroid elements.

Proliferative granulocytes and erythroid precursors were isolated from cell suspensions of human normal bone marrow by sedimentation on an isokinetic gradient of continuous low-density Ficoll. A fivefold enrichment with a 70% recovery of the proliferative granulocyte cohort and of early erythroid elements was achieved, as determined by differential morphology and tritiated thymidine incorporation. Viability and in vitro proliferative capacity following gradient centrifugation remained intact. This method of cell separation, based on differences in cell diameter, affords a simple and rapid means for the purification of specific cell populations from heterologous human normal bone marrow.

Chemotherapy of leukemia in mice, rats, and humans relating time of humoral stimulation, tumor growth, and clinical response.

Studies were conducted in the leukemic mouse and rat to test the hypothesis that enhanced effects of drugs given in sequence relate to a predictable increase in tumor growth and sensitivity to cycle-active agents. The rationale is based on a) evidence that, following drug-induced aplasia, resultant bone marrow proliferation in vivo corresponds temporally with induced humoral stimulatory activity, and on b) models that demonstrate increased cytotoxicity of beta-cytosine arabinoside (Ara-C) to myeloblasts cultured in humoral stimulatory activity (HSA). CD2F1 mice bearing L-1210 leukemia received a course of 60 mg Ara-C/kg every 8th hour (q.8 h) three times on day 0 and on another day in sequence (0,1 through 0,7). The longest survival (250% of controls) was in animals whose second course began on day 3, the time of peak HSA as measured by DNA synthesis induced in L-1210 cells in culture. LBN rats bearing acute myelocytic leukemia (AML) were treated with 100 mg Ara-C/kg q.8 h six times beginning on day 0 and on other days in sequence (0,1 through 0,12). The longest survival was in those treated on day 0,6 (760% of controls), the time of peak serum stimulation, and tumor labeling index (LI). Thirty-seven patients with AML received a single course of therapy with 45 mg Ara-C/kg by a 72-hour infusion and 1.0 mg daunorubicin/kg every day three times. On day 8, the time of peak HSA and tumor LI, Ara-C was again infused. Complete remission was achieved in 56% (65% of all patients less than 60 yr old) with a single cycle of therapy. Median duration of chemotherapy-free remission was 10 months. Of 11 relapsing patients, 8 achieved a second remission with the same regimen. These studies demonstrated that the amount of proliferation of residual tumor and thereby sensitivity to cycle-active drugs given in sequence relates to the initial drug effect on tumor proliferation and the induction of humoral stimulation.

The secondary leukemias: challenges and research directions.

Acute myelogenous leukemia (AML) arising following exposure to genotoxic agents has been recognized as a distinctive entity for more than 40 years. Secondary, or therapy-related, AML accounts for 10%-20% of all AML cases. This review addresses four overarching areas of investigation focused on secondary AMLs: 1) dissection of the molecular structure of the induced genetic lesions and identification of the functional consequences of these changes, thereby providing clues to the pathogenesis of secondary AML and potentially serving as a basis for innovative therapeutic interventions; 2) identification and characterization of mechanisms of DNA damage and the orderly repair of such damage; 3) identification and application of accurate biomarkers of leukemogenesis for the purpose of risk prediction and quantification, potentially allowing recognition of patients especially susceptible to the leukemogenic effects of chemotherapy (for genetic or acquired reasons) and allowing their treatment for cancer to be modified on the basis of this susceptibility; and 4) design and implementation of longitudinal clinical and genetic monitoring of high-risk populations (i.e., individuals under-going cytotoxic therapies for primary cancers). This review of the literature relating to these areas builds upon these themes and attempts to synthesize these seemingly disparate areas of research so that they can be more effectively utilized together to address the problem of secondary AML. Ultimately, the evaluation of these areas will improve our understanding of de novo leukemia and will serve as a springboard for the development of new concepts of therapy and prevention.

Potential role of tamoxifen in prevention of breast cancer.

Despite advances in early detection and treatment of breast cancer, primary prevention has not been well explored, especially for women at increased risk of disease due to reproductive factors and family history. There are, however, suggestions that primary prevention of breast cancer may be a realistic objective. Randomized clinical trials of adjuvant therapy for early-stage breast cancer have demonstrated a 35% decrease in contralateral breast cancers among women receiving tamoxifen compared with controls, suggesting a potential role for tamoxifen in chemoprevention of breast cancer in women at increased risk of the disease. Adjuvant therapy studies also demonstrate that tamoxifen is well tolerated by most patients and suggest additional health benefits from alterations in plasma lipid levels and stabilization of bone mineral loss in women receiving tamoxifen. Aspects of tamoxifen pharmacology, laboratory research, and clinical experience which support its investigation as a chemopreventive agent for breast cancer are summarized, and potential toxic effects are discussed.

Induction of programmed cell death in Kaposi's sarcoma cells by preparations of human chorionic gonadotropin.

BACKGROUND: Isolation of the first neoplastic acquired immunodeficiency syndrome-related Kaposi's sarcoma (KS) cell line (KS Y-1) has furthered understanding of the pathogenesis of KS. Studies with KS Y-1 cells have indicated that inhibition of KS cell proliferation occurs in early pregnancy in mice and after treatment with certain commercial preparations of human chorionic gonadotropin (hCG, a pregnancy hormone purified from urine). The activity of the commercial preparations has been attributed to an hCG-associated factor(s) (HAF). While several clinical benefits of HAF are clearly evident, the basis for its anti-KS properties remains unknown. We investigated the apoptosis-inducing effects of HAF and the expression of apoptosis-related proteins in KS cells. METHODS: KS Y-1 and KS SLK cells were treated with clinical-grade crude preparations of hCG, recombinant hCG, or urine fractions exhibiting anti-KS activity and then examined for features of apoptosis. Levels of proteins associated with apoptosis were monitored by western blot analysis, and cell DNA content was assessed by flow cytometry. Tumors induced in mice by inoculation of KS Y-1 cells were treated with preparations of hCG, and the tumors were examined for cell morphology and also for DNA fragmentation by use of the terminal deoxynucleotidyl transferase-mediated digoxigenin-deoxyuridine triphosphate nick-end-labeling (TUNEL) assay. RESULTS: The HAF present in some preparations of hCG and in urine fractions has the ability to induce apoptosis in KS cells in vitro and in vivo. HAF-triggered apoptosis was preceded by increased levels of the apoptosis-related proteins c-Myc and c-Rel and cell accumulation in Go/G1 phase of the cell cycle. KS Y-1 cells transfected with a c-Myc complementary DNA showed elevated rates of apoptosis. CONCLUSION: The anti-KS activity of HAF appears to induce apoptosis. Such activity suggests a role for HAF in pregnancy-related regulation of cell death.

Growth response of residual leukemia after initial drug therapy.

Clinical trials with laboratory correlates were conducted in patients with acute leukemia to determine if relationships exist between drug dose and growth of surviving leukemia cells. The therapeutic design was based on findings in the leukemic rat that relate the initial dose of drug and tumor kill to the magnitude of residual tumor proliferation and sensitivity to a second drug. Patients with acute myelocytic leukemia received cytarabine, either 2 or 6 g/m2/72 h by continuous infusion. The presence and magnitude of change between initial and residual tumor after treatment, as measured by change in labeling indices, depended on the "priming" dose of drug. The amount of perturbation correlated with clinical response to cytarabine given at the time of induced proliferation. With results which parallel the rat data, the direct relationship of initial drug dose and proliferation of residual tumor is demonstrated in humans, and lends support to the design of our clinical trials of timed sequential therapy.

Enhancement of drug cytotoxicity by recruitment of leukemic myeloblasts with humoral stimulation.

To demonstrate that the effect of 1-beta-D-arabinofuranosylcytosine can be increased when the leukemic cell growth fraction is augmented by induced humoral factors, bone marrow cells from 14 patients with acute myeloblastic leukemia were studied in vitro. Cells were cultured in either pooled stimulatory serum, obtained from leukemic patients undergoing chemotherapy, or autologous leukemic pre-treatment serum. After 2 days in culture, serum containing 1-beta-D-arabinofuranosylcytosine was added. Cells cultured in stimulatory serum proliferated markedly when compared with cells cultured in pretreatment serum, as measured by tritiated thymidine incorporation into an acid-insoluble precipitate, tritiated thymidine labeling indices, and viable tumor cell counts. The cytotoxic effect of 1-beta-D-arabinofuranosylcytosine was enhanced in those cells initially cultured in stimulatory serum relative to cells initially cultured in pretreatment serum. These studies are consistent with the hypothesis that induced humoral stimulation of acute myeloblastic leukemic cells in vitro recruits a greater tumor growth fraction and thereby increases the cytotoxicity of cycle-dependent drugs.

Influence of humoral regulators on proliferation and maturation of normal and leukemic cells.

Factors that influence the proliferation of marrow elements can be detected in sera. To determine the function and to compare the effect of these factors, cells were obtained from patients with normal and leukemic bone marrows. The effects of drug-induced stimulatory and inhibitory sera and leukemic pretreatment sera over time (0 to 6 days) on proliferation and granulocytic morphology of normal and leukemic bone marrow cells in culture were evaluated. Increased proliferation was associated with stimulatory sera, while inhibitory and leukemic pretreatment sera retarded proliferation of both normal and malignant cells. Exposure of normal proliferative cells to inhibitory or leukemic pretreatment sera yielded the greatest increase in mature granulocyte forms. In contrast, although the proliferative response of leukemic cells to these sera was similar to normal, maturation was minimal. These data suggest that leukemic pretreatment sera are similar to inhibitory sera and are not leukemogenic. Both retard proliferation of normal and leukemic bone marrow cells while enhancing maturation of normal cells. Leukemic myeloblasts, however, cannot be made to mature by these humoral regulators.

Drug induced host factors which stimulate growth of residual leukemia in Lewis x Brown Norway F1 (LEW-BN) rats.

Antitumor synergism occurs with two drugs in sequence when the second drug is given at the time of maximal regrowth of residual leukemia and peak humoral stimulatory activity (HSA). To determine if this enhancement relates to a host derived HSA, studies were conducted in Lewis x brown Norway F1 rats bearing brown Norway myelocytic leukemia. A significant cure rate was observed in rats treated initially with 1-beta-D-arabinofuranosylcytosine and then given injections of 10(6) leukemia cells and treated with a second 2-day course of 1-beta-D-arabinofuranosylcytosine in every-8-h s.c. injections in the 6-day period after the initial drug. No effect on survival of the initial drug or of the second drug given at intervals after day 6 was noted. This result is consistent with the efficacy of treatment at the time of peak HSA and tumor growth. The direct effect of HSA on tumor sensitivity to 1-beta-D-arabinofuranosylcytosine was evaluated by 18-h incubations of leukemia and HSA, followed by bioassay. Increased survival and high cure rates were observed when compared with cultured cells in normal serum. These studies support the notion that host derived factors operative during drug induced aplasia stimulate tumor growth and thereby, if the drugs are properly timed, increase sensitivity to cycle active agents.

Changes in topoisomerase I levels and localization during myeloid maturation in vitro and in vivo.

Changes in topoisomerase I (topo I) levels and localization were examined during the course of granulocytic maturation in vitro and in vivo. Western blotting revealed that granulocytic maturation in DMSO-treated HL-60 human leukemia cells was accompanied by a 5-fold decrease in topo I polypeptide content. Consistent with this result, 3- to 5-fold higher concentrations of the topo I poison camptothecin were required to stabilize topo I-DNA adducts in DMSO-treated HL-60 cells compared to untreated cells. Northern blotting revealed that these changes occurred without any decrease in topo I message. Immunolocalization studies revealed that these quantitative changes were accompanied by redistribution of topo I away from the nucleoli, where it was prominently accumulated in untreated HL-60 cells, to a more uniform nuclear distribution in DMSO-treated cells. Similar changes occurred during granulocytic maturation in human marrow in vivo. Western blotting revealed that topo I levels in normal progranulocytes were 50% as high as those in HL-60 cells, levels in metamyelocytes were 35% as high as HL-60 cells, and levels in peripheral blood granulocytes were 5% as high as HL-60 cells. Two other polypeptides that are concentrated in nucleoli, poly(ADP-ribose) polymerase and B23/nucleophosmin, also decreased during the course of granulocytic maturation. These changes were accompanied by an alteration in topo I localization similar to that observed in HL-60 cells during the course of granulocytic maturation. Conversely, treatment of human lymphocytes with the mitogenic lectin concanavalin A resulted in a 3-fold increase in topo I polypeptide content concomitant with a prominent increase in the amount of nucleolar antigen. These observations not only provide a context for understanding the recent observation that topo I levels are higher in human leukemia specimens than in normal marrow but also raise the possibility that elevated topo I levels in other cells might reflect alterations in nucleolar structure and function.

Direct relationship of marrow cell growth and 1-beta-D-arabinofuranosylcytosine metabolism.

To define the relationship between perturbed cell growth and intracellular metabolism of 1-beta-D-arabinofuranosylcytosine (ara-C) in sensitive human cells, growth kinetic, and biochemical pharmacological determinants were examined in normal human bone marrow populations in vitro in normal serum and in the presence of drug-induced humoral stimulatory activity (HSA). Cells cultured in HSA demonstrated both increased proliferation and greater ara-C-related inhibition of DNA synthesis than did cells maintained in normal serum, as measured by [3H]thymidine incorporation into DNA and [3H]thymidine granulocyte precursor labeling index. Parallel measurements of [3H]ara-C incorporation into DNA demonstrated similar behavior in HSA-perturbed cells. When these cultured cells were exposed to 1 and 10 microM ara-C, intracellular formation of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate over 3 hr and retention of this active form during 1 subsequent hr in drug-free medium were both increased in HSA-stimulated cells relative to cells cultured in normal serum. These studies demonstrate coupling of induced cell growth kinetics with enhanced intracellular metabolism of the S-phase-specific antimetabolite ara-C in normal human marrow cells. The close direct relationship between growth kinetic perturbation and augmentation of intracellular ara-C activation in this normal hematopoietic model provides a basis for comparison with leukemic cell populations, in which uncoupling of growth kinetics and pharmacokinetics may signify divergence from normal drug-sensitive cell behavior and, thus, resistance to ara-C cytotoxicity.

Correlation of proliferative and clonogenic tumor cells in multiple myeloma.

To expand on the findings from previous clinical trials that the growth of residual tumor is increased at a predictable time following initial drug administration, malignant plasma cells from bone marrows of patients with multiple myeloma (MM) were examined for changes in proliferation and clonogenicity induced in vivo by cyclophosphamide and in vitro by drug-induced humoral stimulatory activity. Peak plasma cell [3H]thymidine labeling index (LI) occurred predictably following drug and paralleled changes in agar colony formation by marrow cells obtained during therapy. Colony-forming capacity of pretreatment MM marrow populations was enhanced when those cells were cultured with humoral stimulatory activity, similar to the increased colony formation detected in Day 9 postcyclophosphamide marrows at the time of peak plasma cell LI. To further define a relationship between proliferative plasma cells and colony-forming tumor cells, MM marrows were fractionated by sedimentation on an isokinetic gradient. Enrichment of a proliferative tumor cell cohort was achieved, evidenced by [3H]thymidine LI. Colony-forming cells were also enriched by isokinetic gradient sedimentation, and agar colony formation by MM marrow cell fractions correlated with the kinetic characteristics of the isolated subpopulations. These studies of whole and fractionated human MM marrow cell populations suggest that the kinetically active cells which are induced to proliferate in vivo and in vitro are closely related to the clonogenic tumor cells which produce colonies in agar and which, like those cells measured by [3H]thymidine LI, respond to growth stimulation by drug-induced humoral stimulatory activity.

Topoisomerase II levels during granulocytic maturation in vitro and in vivo.

Western blotting, indirect immunolocalization, flow cytometry, and a functional assay for drug-induced strand breakage were utilized to examine topoisomerase (topo) II levels during granulocytic maturation in HL-60 human progranulocytic leukemia cells and in samples of normal human marrow. Indirect immunofluorescence revealed that the intensity of the signal for topo II in unsynchronized log phase HL-60 cells varied widely. Indirect immunolabeling combined with propidium iodide staining and two-parameter flow cytometry revealed that topo II levels increased an average of 2-fold as cells progressed from G1 to G2/M. When HL-60 cells were induced to mature toward granulocytes, topo II levels progressively decreased and became undetectable by functional assays, by indirect immunoperoxidase staining, and by Western blotting with an antibody which identified Mr 170,000 and Mr 180,000 forms of topo II. Similar changes were detected during normal granulocytic maturation in human marrow in vivo. Western blotting revealed that levels of the Mr 170,000 (proliferation-associated) isoform of topo II were highest in marrow fractions enriched in progranulocytes and myelocytes, intermediate in unfractionated marrow from normal volunteers, and undetectable in mature granulocytes. The Mr 180,000 topo II polypeptide was also diminished or absent from mature granulocytes. In further experiments, marrow samples from normal volunteers were subjected to flow cytometry after labeling of topo II and various cell surface markers. Levels of the Mr 170,000 topo II polypeptide in CD34-positive cells (multipotent and committed progenitors from several hematopoietic lineages) were indistinguishable from levels observed in the HL-60 leukemia cell line. These results suggest that topo II levels in highly proliferative normal human myeloid cells in vivo approach levels found in corresponding neoplastic cell lines in vitro. Conversely, as the same cells mature into granulocytes in vivo or in vitro, levels of both molecular weight forms of topo II diminish. These results provide a framework for the further investigation of topo II levels and drug sensitivity in human leukemia.

Phase I and pharmacodynamic study of taxol in refractory acute leukemias.

Taxol, a novel antimicrotubule agent that enhances tubulin polymerization and microtubule stability, was administered to adults with refractory leukemias as a 24-h i.v. infusion in a Phase I study. The primary objectives were to determine the maximum tolerated dose of taxol administered on this schedule to patients with acute leukemias and describe the nonhematological toxicities which became dose limiting. The starting dose, 200 mg/m2, was based on the maximum tolerated dose in solid tumor trials, in which myelosuppression precluded dose escalation. Seventeen patients received 28 evaluable courses at 200, 250, 315, and 390 mg/m2. Severe mucositis limited further dose escalation. Other nonhematological effects included peripheral neuropathy, alopecia, myalgias, arthralgias, nausea, vomiting, diarrhea, and an acute pulmonary reaction that was presumptively due to taxol's Cremophor vehicle. Mean peak taxol plasma concentrations at all dose levels were in the range of concentrations that were previously demonstrated to induce microtubule bundles, a morphological effect associated with cytotoxicity, in leukemia cells in vitro. Pretreatment blasts from 12 patients were incubated with taxol ex vivo. Taxol-induced microtubule bundles were apparent in the blasts of eight patients who also had cytoreduction of tumor, and sensitivity to bundle formation was related to the magnitude of antitumor activity. In contrast, taxol did not induce microtubule bundles ex vivo in the blasts of the other four total nonresponders. Based on this study, the maximum tolerated doses and recommended Phase II doses for taxol, limited by nonhematological toxicity and administered as a 24-h i.v. infusion to patients with refractory leukemias, are 390 and 315 mg/m2. Phase II trials at these myelosuppressive doses are required to determine taxol's activity in the treatment of leukemias. In addition, further evaluation of microtubule bundle formation ex vivo in Phase II studies is necessary to determine the ultimate utility of this assay in assessing tumor sensitivity to taxol.

Association of reduced total iron binding capacity and fungal infections in leukemic granulocytopenic patients.

Serum total iron-binding capacity (TIBC) was measured serially on 70 patients with acute leukemia throughout the period of chemotherapy-induced granulocytopenia. Fungal infections were documented in 13 of these patients (18.6%), while 41 patients (58.6%) had clinically suspected fungal infections and 16 (22.9%) had no evidence of fungal infections during the granulocytopenia. Documented fungal infection occurred in patients with the greatest reduction in TIBC (P less than .015). Early reduction in TIBC also correlated with a greater risk for occurrence of fungal infection, and the earliest institution of amphotericin B (Amp-B) (P less than .004). Effective antifungal therapy was further associated with a return of TIBC levels toward normal. These data demonstrate that altered iron metabolism during granulocytopenia is associated with the development of fungal infections in compromised patients. Serial monitoring of TIBC, along with other clinical and mycologic findings, may prove useful in developing strategies for predicting patients at risk for developing a fungal infection and directing the appropriate use of empiric therapy with Amp-B.